Screw and screw driver

ABSTRACT

Various screws and corresponding screwdrivers are disclosed. For example, in one embodiment a screwdriver having a single, circular, non-axial pin is disclosed, and a corresponding screw having a single, circular, non-axial bore is disclosed. In another embodiment, a screwdriver (and corresponding screw) having a plurality of pins arranged asymmetrically about the central axis of the screwdriver is disclosed. In yet another embodiment, a screwdriver (and corresponding screw) having an irregularly-shaped and centrally-located pin is disclosed. Techniques for combining these and other features in various ways are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a divisional application of commonly-ownedU.S. patent application Ser. No. 10/385,133, filed on Mar. 10, 2003,entitled “Screw and Screw Driver”.

BACKGROUND

[0002] 1. Field of the Invention

[0003] The present invention relates to screws and screw drivers and,more particularly, to screws and screwdrivers of the bore and pinvariety.

[0004] 2. Related Art

[0005] Various kinds of screws and screw drivers are well known in theart. Referring to FIG. 1, for example, a conventional flat-headscrewdriver 100 and slot-head screw 108 are shown. The screwdriver 100includes a generally cylindrical grip 102, a cylindrical shank 104, anda flat tapered blade 106 aligned along a central axis 130. The screw 108includes a generally flat and round head 110 at the end of a shank 114.A slot 112 bisects the surface of the head 110.

[0006] The screwdriver 100 may be grasped by the grip 102 and the blade106 guided to engage the slot 112. Torque may then be applied, typicallyin a clockwise direction 118, to drive the screw 108 through a material(not shown). Threads 116 on the shank 114 of the screw 108 provide addedshear for driving the screw 108.

[0007] One problem with the conventional flat-head screwdriver 100 isthat the blade 106 is susceptible to slippage within the slot 112. Smallamounts of slippage make it more difficult to drive the screw 108, whilelarger amounts of slippage may cause the blade 106 to disengage from theslot 112 entirely. After each such disengagement, the blade 106 mustmanually be reengaged in the slot 112, making the process of driving thescrew 108 tedious and time-consuming. The problem of slippage may bemitigated by shortening the length of the slot 112, but at the cost ofreducing the torque applied to the screw 108 and making it moredifficult to engage the blade 106 in the slot 112. Although conventionalPhillips-head screws and screwdrivers address the problem of slippage byincorporating cross-shaped slot and screwdriver heads, they present thesame difficulty of initially positioning the screwdriver blade withinthe screw slot.

[0008] Referring to FIG. 2A, a conventional dual-pin screwdriver 200 isshown for use with a dual-bore screw 208. Like the conventionalflat-head screwdriver 100, the dual-pin screwdriver 200 includes agenerally cylindrical grip 202 and a cylindrical shank 204. Instead of ablade, however, the screwdriver 200 includes a pair of opposing pins 206a-b, spaced equidistant from central axis 230.

[0009] Like the flat-head screw 108, the screw 208 includes a generallyflat and round head 210 at the end of a shank 214. Instead of a slot,however, the screw 208 includes a pair of opposing cylindrical bores 212a-b, spaced equidistant from central axis 230.

[0010] The screwdriver 200 may be grasped by the grip 202 and the pins206 a-b guided so that they engage bores 212 a and 212 b, respectively.Torque may then be applied, typically in a clockwise direction 218, todrive the screw 208 through a material (not shown). Threads 216 on theshank 214 of the screw 208 provide added shear for driving the screw208.

[0011] Although the screwdriver 200 and screw 208 solve the problem oflateral slippage, their use requires that the two pins 206 a-b bemanually engaged in the two bores 212 a-b. This may require significanthand-eye coordination and therefore make the process of engaging thescrewdriver 200 with the screw 208 difficult.

[0012] Referring to FIG. 2B, a conventional single-pin screwdriver 250is shown for use with a single-bore screw 258. The single-pinscrewdriver 250 includes a generally cylindrical grip 252 and acylindrical shank 254. Instead of two pins, however, the screwdriver 250includes a single centrally-located pin 256 having a squarecross-section. Although conventional screwdrivers of this variety mayuse shapes other than squares (such as hexagons), to apply the necessarytorque the pin 256 must not be circular.

[0013] Screw 258 includes a generally flat and round head 260 at the endof a shank 264. The screw 258 includes a single bore 262 located alongcentral axis 280.

[0014] The screwdriver 250 may be grasped by the grip 252 and the pin256 guided so that it engages bore 262. Torque may then be applied,typically in a clockwise direction 268, to drive the screw 258 through amaterial (not shown). Threads 266 on the shank 264 of the screw 258provide added shear for driving the screw 258.

[0015] Referring to FIG. 3, a conventional square-head screwdriver 300is shown for use with a square-head screw 308. Like the conventionalflat-head screwdriver 300, the square-head screwdriver 300 includes agenerally cylindrical grip 302 and a cylindrical shank 304. Instead of ablade, however, the screwdriver 300 includes a hollow square head 306forming a cavity 332 having a square cross-section. The screw 308includes a square head 310 at the end of a shank 314.

[0016] The screwdriver 300 may be grasped by the grip 302 and thescrewdriver head 306 guided so that it engages the screw head 310.Torque may then be applied, typically in a clockwise direction 318, todrive the screw 308 through a material (not shown). Threads 316 on theshank 314 of the screw 308 provide added shear for driving the screw308. The heads 306 and 310 may be polygonal shapes other than squares,such as hexagons.

[0017] Although the screwdriver 300 and screw 308 are easier to engageand are less prone to slippage than the screwdrivers 100 and 200 andscrews 108 and 208 illustrated in FIGS. 1 and 2, respectively, thesquare head 310 of the screw 308, when exposed on the surface into whichthe screw 308 has been driven, may present a facade that is lessaesthetically pleasing than the circular face of the flat-head screw108. Screws having circular faces, however, require slots (as in thecase of the slot 112 in the flat-head screw 108), dual and symmetricalopposing bores (as in the case of the bores 212 a-b in the screw 208),or a central but non-circular bore (as in the case of the bore 262 inthe screw 258) to apply the techniques of the prior art. Screws havingsuch features have the disadvantages described above.

[0018] What is needed, therefore, is a combination of screw andscrewdriver which are easily engaged with each other, not prone toslippage, and which result in an aesthetically pleasing exposed screwface.

SUMMARY

[0019] Various screws and corresponding screwdrivers are disclosed. Forexample, in one embodiment a screwdriver having a single, circular,non-axial pin is disclosed, and a corresponding screw having a single,circular, non-axial bore is disclosed. In another embodiment, ascrewdriver (and corresponding screw) having a plurality of pinsarranged asymmetrically about the central axis of the screwdriver isdisclosed. In yet another embodiment, a screwdriver (and correspondingscrew) having an irregularly-shaped and centrally-located pin isdisclosed. Techniques for combining these and other features in variousways are also disclosed.

[0020] One aspect of the present invention features a screw thatincludes a threaded shank having a lengthwise central axis and a headcoupled to one end of the shank. The head includes a forward surface anda single bore. The single bore defines a region forming a gap in theforward surface. The centroid of the region is located a non-zerodistance from the central axis. The bore may, for example, be circular.Another aspect of the present invention features a screwdriver fordriving the screw just described. The screwdriver includes a grip, ashank coupled at one end to the grip and having a first lengthwisecentral axis, and a single pin coupled to the other end of the shank andhaving a second lengthwise central axis, wherein the first and secondlengthwise central axes are not coincident. The screwdriver may includea head coupled at a first end to the other end of the shank and at asecond end to the single pin. The head may include a guide-skirt havingan inner surface defining a depression in the head, and the single pinmay extend outward from the depression.

[0021] Another aspect of the present invention features a screwincluding a threaded shank having a lengthwise central axis and a headcoupled to one end of the shank. The head includes a forward surface andat least two bores, which may be circular, non-circular, or acombination thereof. The at least two bores define at least two regionsforming at least two gaps in the forward surface. The centroids of theat least two regions are located asymmetrically about the central axis.In another aspect of the present invention, a screwdriver is providedwhich includes pins appropriately shaped and arranged to engage thebores of the screw just described.

[0022] Another aspect of the present invention features a screwincluding a threaded shank having a lengthwise central axis and a headcoupled to one end of the shank. The head includes a forward surface andat least one bore. The at least one bore defines at least one regionforming at least one gap in the forward surface. The at least one regionhas an outline (such as a letter of the alphabet) that is not a regularpolygon. In another aspect of the present invention, a screwdriver isprovided which includes one or more pins appropriately shaped andarranged to engage the one or more bores of the screw just described.

[0023] Another aspect of the present invention features a screwincluding a threaded shank having a lengthwise central axis and a headcoupled to one end of the shank. The head includes a forward surface andat least three bores. The at least three bores define at least threeregions forming at least three gaps in the forward surface. Thecentroids of the at least three regions are located symmetrically aboutthe central axis. In another aspect of the present invention, ascrewdriver is provided which includes pins appropriately shaped andarranged to engage the bores of the screw just described.

[0024] Other features and advantages of various aspects and embodimentsof the present invention will become apparent from the followingdescription and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025]FIG. 1 is a perspective view of a prior art flat-head screwdriverand screw;

[0026]FIG. 2A is a perspective view of a prior art dual-pin screwdriverand screw;

[0027]FIG. 2B is a perspective view of a prior art single-pinscrewdriver and screw;

[0028]FIG. 3 is a perspective view of a prior art square-headscrewdriver and screw;

[0029]FIG. 4 is a perspective view of a single-pin screwdriver accordingto a first embodiment of the present invention;

[0030]FIG. 5 is a perspective view of a single-bore screw for use withthe screwdriver of FIG. 4 according to the first embodiment of thepresent invention;

[0031]FIG. 6 is a perspective view of the screwdriver of FIG. 4 inengagement with the screw of FIG. 5 according to the first embodiment ofthe present invention;

[0032]FIG. 7 is a perspective view of a single-pin screwdriver accordingto a second embodiment of the present invention;

[0033]FIG. 8 is a perspective view of a single-bore screw for use withthe screwdriver of FIG. 4 according to the second embodiment of thepresent invention;

[0034]FIG. 9 is a perspective view of the screwdriver of FIG. 4 inengagement with the screw of FIG. 5 according to the second embodimentof the present invention;

[0035]FIG. 10 is a perspective view of a single-pin screwdriveraccording to a third embodiment of the present invention;

[0036]FIG. 11 is a perspective view of a single-bore screw for use withthe screwdriver of FIG. 10 according to the third embodiment of thepresent invention; and

[0037]FIG. 12 is a perspective view of the screwdriver of FIG. 10 inengagement with the screw of FIG. 11 according to the second embodimentof the present invention.

DETAILED DESCRIPTION

[0038] Referring to FIG. 4, a single-pin screwdriver 400 is shownaccording to one embodiment of the present invention. The screwdriver400 includes a generally cylindrical grip 402, a cylindrical shank 404,and a head 406. A guide-skirt 411 on the head 406 has an inner surface410 which defines a depression for engaging a corresponding screw (seeFIG. 5, below). Central axis 414 intersects surface 412 at the center416 of surface 412. A single non-axial pin 408 extends from forwardsurface 412 of head 406. Pin 408 is offset from center 416 by a distancewhich may be freely chosen.

[0039] Referring to FIG. 5, a single-bore screw 420 is shown for usewith the screwdriver 400 according to one embodiment of the presentinvention. The screw 420 includes a generally flat and round head 422 atthe end of a shank 426. The screw 420 includes a single cylindrical bore424 extending into the head 422 from forward surface 434 of head 422.Central axis 430 intersects surface 434 at the center 432 of surface434. Bore 424 is offset from center 432 by a distance which is equal tothe distance of pin 408 from the center 416 of the forward surface 412of the screwdriver 400 (FIG. 4). Bore 424 may or may not penetratethrough the full depth of head 422, may or may not overlap in whole orin part with the shank 426, and may or may not penetrate into the shank426.

[0040] Referring to FIG. 6, the screwdriver 400 of FIG. 4 is shown inengagement with the screw 420 of FIG. 5 according to one embodiment ofthe present invention. The screwdriver 400 may be grasped by the grip402 and the head 406 guided so that the pin 408 engages the bore 424 andso that the screw head 422 engages the depression in the screwdriverhead 406. The inner diameter of the guide-skirt 411 is equal to orslightly larger than the diameter of the screw head 422.

[0041] Torque may then be applied to the grip 402, typically in aclockwise direction 440 about central axis 414. Torque is transferredthrough the pin 408 to the inner surface of bore 424, thereby causingthe screw 420 to rotate and be driven through a material (not shown).Threads 428 on the shank 426 of the screw 420 provide added shear fordriving the screw 420. Engagement of the screw head 422 in theguide-skirt 411 prevents lateral slippage of the screw 420 while it isbeing driven.

[0042] The limits of the torque applied by the screwdriver 400 derivefrom materials strengths and dimensions. In particular, the shearstrength of the pin or bore materials must be matched to the forcesapplied. If the width of the screwdriver skirt loll is minimized inorder to allow close spacing between screw heads and mechanicalobstacles, then the strength of the skirt 1011 must be carefullyaccounted for as well. In general, the pin and skirt materials should beharder than the bore material since the screwdriver 400 is typicallyused to drive many screws and therefore must be more durable than thebore material against both wear and accidental breakage. The shearforces on the pin 408 and bore 424 are directly proportional to thetorque applied divided by the distance from the bore 424 and pin 408 tothe central axis 1014. Thus, given constant constraints on materials,designs in which the bore 424 and pin 408 are farther from the centralaxis 1014 will allow greater torque to be applied to driving the screw420. Shear strength of the pin 408 and bore 424 also increase withincreasing cross-sectional area. Therefore, larger-diameter pins andbores will allow greater torques to be applied.

[0043] Referring to FIG. 7, a single-pin screwdriver 700 is shownaccording to one embodiment of the present invention. Like thescrewdriver 400 illustrated in FIG. 4, the screwdriver 700 includes agenerally cylindrical grip 702, a cylindrical shank 704, and a head 706.A guide-skirt 711 on the head 706 has an inner surface 710 which definesa depression for engaging a corresponding screw (see FIG. 8, below). Aswith screwdriver 400, central axis 714 intersects surface 712 at thecenter 716 of surface 712. A single non-axial pin 708 extends fromforward surface 712 of head 706. Pin 708 is offset from center 716 by adistance which may be freely chosen.

[0044] Unlike pin 408, which is free-standing, pin 708 abuts innersurface 710 and may even be molded integrally with inner surface 710 sothat pin 708 effectively forms a protuberance extending from innersurface 710. If, however, screwdriver 700 is implemented without theguide-skirt 711, the pin 708 may be implemented as a free-standing pinhaving a circular or semi-circular cross-section.

[0045] Referring to FIG. 8, a single-bore screw 720 is shown for use inconjunction with the screwdriver 700 according to one embodiment of thepresent invention. The screw 720 includes a generally flat and roundhead 722 at the end of a shank 726. The screw 720 includes a singlesemi-circular notch 724 extending from the outer edge of forward surface434 of head 422. Central axis 730 intersects surface 734 at the center732 of surface 734. Although bore 724 is semi-circular in shape, it isdefined in cross-section by a circle which is offset from center 732 bya distance which is equal to the distance of pin 708 from the center 716of the forward surface 712 of the screwdriver 700 (FIG. 7).

[0046] Referring to FIG. 9, the screwdriver 700 of FIG. 7 is shown inengagement with the screw 720 of FIG. 8 according to one embodiment ofthe present invention. The use of the screwdriver 700 to drive the screw720 may be understood by reference to the description above with respectto FIG. 6.

[0047] Referring to FIG. 10, a single-pin screwdriver 1000 is shownaccording to one embodiment of the present invention. Like thescrewdriver 400 illustrated in FIG. 4, the screwdriver 1000 includes agenerally cylindrical grip 1002, a cylindrical shank 1004, and a head1006. An optional guide-skirt 1011 on the head 1006 has an inner surface1010 which defines a depression for engaging a corresponding screw (seeFIG. 11, below). A single pin 1008 extends from forward surface 1012 ofhead 1006. As with screwdriver 400, central axis 1014 intersects surface1012 at the center 1016 of surface 1012. Pin 1008 is located centrallyon the axis 1014. Alternatively, pin 1008 may be offset from center 1016by a distance which may be freely chosen.

[0048] In the example illustrated in FIG. 10, the cross-section of pin1008 is in the shape of the letter “A.” The pin 1008 may, however, haveany shape, such as a letter of the alphabet, a heart shape, or acorporate logo. As illustrated below with respect to FIG. 11, the pin1008 is shaped to engage a screw including a depression having a shapecorresponding to the shape of the pin 1008.

[0049] Referring to FIG. 11, a single-bore screw 1020 is shown for usein conjunction with the screwdriver 1000 according to one embodiment ofthe present invention. The screw 1020 includes a generally flat andround head 1022 at the end of a shank 1026. The screw 1020 includes asingle centrally-located depression 1024 extending into head 1022 fromforward surface 1034 of head 1022. Central axis 1030 intersects surface1034 at the center 1032 of surface 1034.

[0050] In the example illustrated in FIG. 11, the depression 1024 is inthe shape of the letter “A,” thereby to engage the pin 1008 of thescrewdriver 1000. The depression 1024, however, may have any shape, suchas a letter of the alphabet, a heart shape, or a corporate logo. Moregenerally, the depression 1024 may be in the shape of a silhouette of animage desirable for aesthetic reasons. Note that the depression 1024may, for example, be so far offset from the central axis 1014 that theletter “A” is effectively cropped by the outer edge of the head 1022,resulting in a bore (and corresponding pin) whose shape is that portionof the letter “A” which falls within the boundary defined by the outeredge of the head 1022.

[0051] Although the depression 1024 illustrated in FIG. 11 extends onlypartway through the head 1022 of the screw 1020, the depression 1024 mayextend fully through the screw 1020, in which case the depression 1024is a bore. Furthermore, the depression 1024 need not be centrallylocated. Rather, the depression 1024 (and the corresponding pin 1008)may be offset from the center 1032 by a distance which may be freelychosen.

[0052] Referring to FIG. 12, the screwdriver 1000 of FIG. 10 is shown inengagement with the screw 1020 of FIG. 11 according to one embodiment ofthe present invention. When the pin 1008 and depression 1024 are notcentrally located, the use of the screwdriver 1000 to drive the screw1020 may be understood by reference to the description above withrespect to FIG. 6. When the pin 1008 and depression 1024 are centrallylocated, as illustrated in FIGS. 10-12, the torque is transferredthrough the head 1006 to the inner surfaces of depression 1024, therebycausing the screw 420 to rotate and be driven through a material (notshown). When the pin 1008 and depression 1024 are centrally located, andassuming that the center of torque of the driving pattern is concentricwith the central axis of the screw, then the guide skirt 1011, whilepossibly desirable in some cases for ease of alignment, etc., is notnecessary since the torque is conveyed entirely by the driving pattern.

[0053] The embodiments illustrated in FIGS. 4-12 above are illustrativeonly and do not constitute limitations of the present invention. Rather,various other embodiments fall within the scope of the claims below. Forexample, the cross-sections of pin 408 and bore 424 need not becircular, but rather may be any shape, such as a triangle, square,rectangle, arc, or heart.

[0054] Similarly, the cross-sections of pin 708 and notch 724 need notbe circular sections, but rather may be any shape, such as a rectangle,“V,” or oval. Other cross-sectional shapes that may be used include, butare not limited to, the following: clovers, spades, diamonds, hearts,clubs, fleur d'alis, musical notes or instruments, depictions of themoon (e.g., half-moons or quarter-moons) or sun, leaves (such as mapleleaves or oak leaves), flags, portraits, flowers or other plants,animals, machinery or components thereof, seashells, snowflakes, sportsequipment, geographical features (such as outlines of countries,states), stars, letters or words in any language, alchemical symbolsrepresenting elements from the periodic table, signs of the zodiac,traffic sign shapes (e.g., one way, U-turn, caution), emoticons (e.g.,happy face, sad face, mad face), mathematical symbols, ideographs, andany combination thereof. Furthermore, the pins 408 and 708, bore 424,and notch 724 may be any size.

[0055] In the following discussion, references to the pin 408 may alsobe applicable to the other pins and heads disclosed herein (such asthose illustrated in FIGS. 7-12), and any references to the bore 424 mayalso be applicable to the bores, notches, and depressions disclosedherein (such as those illustrated in FIGS. 7-12). The pin 408 and bore424 may be any distance from the center points 416 and 432,respectively. The present invention is not limited to screws andscrewdrivers having the numbers of pins/bores shown in FIGS. 4-12.Furthermore, the present invention is not limited to screws andscrewdrivers having pins/bores arranged in the particular spatialconfigurations shown in FIGS. 4-12.

[0056] For example, a screw may include both a plurality of boresarranged symmetrically about the central axis of the screw head and oneor more additional bores which are not symmetrically arranged about thecentral axis. Alternatively, the screw may include a centrally-located(circular or non-circular) bore in addition to one or more non-centrallylocated (and optionally non-symmetrical) bores. Alternatively, the screwmay include a set of three or more (circular or non-circular) boresarranged symmetrically about the central axis. Alternatively, forexample, there may be three pins in a “Y” or “V” configuration, or fourpins in a rectangular configuration, with bores in a correspondingconfiguration.

[0057] There may be fewer pins on the screwdriver 400 than bores on thescrew 420. For example, there may be one pin and three bores, therebyobtaining the advantages of the screwdriver 400 and screw 420illustrated in FIGS. 4 and 5, respectively, with the additionaladvantage of facilitating the engagement of the screwdriver 400 in thescrew 420. A single screwdriver 400 may therefore be used with screwshaving different numbers of bores in different configurations, so longas a subset of the bores on each screw are located to allow engagementwith the screwdriver pin(s).

[0058] The screwdriver 400 may be implemented with a head having a flatforward surface rather than the guide-skirt 411 illustrated in FIG. 4.Although the pin 408 and bore 424 illustrated in FIGS. 4 and 5,respectively, are cylindrical, the pin(s) and bore(s) may be any shape.Furthermore, a single screwdriver may include pins of varying shape. Asingle screw may include both bores and notches in any combination andconfiguration.

[0059] The bore 424 need not fully extend through the screw head 422.The pin 408 may be longer or shorter than the corresponding bore. Forexample, a pin that is longer than the bore through which it extends mayprovide extra stability and therefore eliminate or reduce the need forthe guide-skirt 411. Such an extended pin may, for example, extend intothe shank 426 of the screw 420. The pin 408 need not be fixed inlocation or length. For example, the pin 408 may be partially orentirely retractable. Examples of centrally-located retractable pins aredisclosed in U.S. Pat. No. 4,314,489 to Arcangeli, entitled“Screwdrivers,” issued on Feb. 9, 1982.

[0060] It should be appreciated that each screw feature described aboveimplicitly define complementary screwdrivers and vice versa.

[0061] Among the advantages of the invention are one or more of thefollowing.

[0062] The non-central location of the pin 408 and bore 424 allow torqueto be transferred from the screwdriver 400 to the screw 420 using asingle pin/bore combination. One advantage of using a single pin/borecombination is that it may simplify and reduce the cost of designingand/or manufacturing the screwdriver 400 and screw 420. Anotheradvantage of the screws and screwdrivers disclosed herein, which isparticularly applicable to coarsely threaded screws, is that the screwcan be engaged in an exactly known rotational phase of the screwdriver,a property that is not shared by conventional screwdrivers that have2-fold (slot), 3-fold, 4-fold (Robertson), 5-fold (Allen), or 6-fold(Allen) rotational symmetries.

[0063] A further advantage of using a single pin/bore combination isthat the screw 420, once driven into the desired material, presents asurface (i.e., forward surface 434) exposing the single bore 424. One ormore screws exposing such surfaces may present a more aestheticallypleasing facade than screws having slotted surfaces or surfaces havingdual opposing bores. Furthermore, as described above, screws withvarious numbers of bores having various shapes and arranged in variousconfigurations may be implemented in accordance with the presentinvention, thereby presenting further opportunities for increasing theaesthetic appeal of the surface on which the screws are exposed.

[0064] It is to be understood that although the invention has beendescribed above in terms of particular embodiments, the foregoingembodiments are provided as illustrative only, and do not limit ordefine the scope of the invention. Various other embodiments, includingbut not limited to the following, are also within the scope of theclaims.

What is claimed is:
 1. A screwdriver comprising: a grip; a shank coupledat one end to the grip and having a first lengthwise central axis; and asingle pin coupled to the other end of the shank and having a secondlengthwise central axis, wherein the first and second lengthwise centralaxes are not coincident.
 2. The screwdriver of claim 1, furthercomprising: a head coupled at a first end to the other end of the shankand at a second end to the single pin.
 3. The screwdriver of claim 2,wherein the head comprises a guide-skirt having an inner surfacedefining a depression in the head, and wherein the single pin extendsoutward from the depression.
 4. The screwdriver of claim 3, wherein thepin comprises a protuberance on the inner surface.
 5. The screwdriver ofclaim 1, wherein the first central axis does not intersect any portionof the single pin.
 6. The screwdriver of claim 1, wherein across-section of the single pin is circular.
 7. The screwdriver of claim1, wherein the pin abuts an outer edge of the head.
 8. The screwdriverof claim 1, wherein the pin is retractable into the shank.
 9. Ascrewdriver comprising: a grip; a shank coupled at one end to the gripand having a first lengthwise central axis; and at least two pinscoupled to the other end of the shank and having at least two secondlengthwise central axes, the at least two pins being locatedasymmetrically about the first lengthwise central axis.
 10. Thescrewdriver of claim 9, further comprising: a head coupled at a firstend to the other end of the shank and at a second end to the at leasttwo pins.
 11. The screwdriver of claim 10, wherein the head comprises aguide-skirt having an inner surface defining a depression in the head,and wherein the at least two pins extend outward from the depression.12. The screwdriver of claim 11, wherein at least one of the at leasttwo pins comprises a protuberance on the inner surface.
 13. Thescrewdriver of claim 9, wherein the first central axis does notintersect any portion of any of the at least two pins.
 14. Thescrewdriver of claim 9, wherein a cross-section of at least one of theat least two pins is circular.
 15. The screwdriver of claim 9, whereinthe at least two pins abut an outer edge of the head.
 16. Thescrewdriver of claim 9, wherein at least one of the at least two pins isretractable into the shank.
 17. The screwdriver of claim 9, furthercomprising a pin located having a central axis coincident with the firstlengthwise central axis.
 18. The screwdriver of claim 9, furthercomprising a plurality of pins located symmetrically about the firstlengthwise central axis.
 19. A screwdriver comprising: a grip, a shankcoupled at one end to the grip and having a first lengthwise centralaxis; and at least one pin coupled to the other end of the shank andhaving at least one second lengthwise central axis, the pin comprising apin head having an outline that is not a regular polygon.
 20. Thescrewdriver of claim 19, wherein the first central axis is notcoincident with any of the at least one central axis.
 21. Thescrewdriver of claim 19, wherein the first central axis is coincidentwith at least one of the at least one central axis.
 22. The screwdriverof claim 19, further comprising: a head coupled at a first end to theother end of the shank and at a second end to the at least one pin. 23.The screwdriver of claim 20, wherein the head comprises a guide-skirthaving an inner surface defining a depression in the head, and whereinthe at least one pin extends outward from the depression.
 24. Thescrewdriver of claim 23, wherein the at least one pin comprises at leastone protuberance on the inner surface.
 25. The screwdriver of claim 19,wherein a cross-section of at least one of the at least one pin iscircular.
 26. The screwdriver of claim 19, wherein the at least one pinabuts an outer edge of the head.
 27. The screwdriver of claim 19,wherein at least one of the at least one pin is retractable into theshank.
 28. A screwdriver comprising: a grip; a shank coupled at one endto the grip and having a first lengthwise central axis; and at leastthree pins coupled to the other end of the shank and having at leastthree second lengthwise central axes, the at least three pins beinglocated symmetrically about the first lengthwise central axis.
 29. Thescrewdriver of claim 28, further comprising: a head coupled at a firstend to the other end of the shank and at a second end to the at leastthree pins.
 30. The screwdriver of claim 29, wherein the head comprisesa guide-skirt having an inner surface defining a depression in the head,and wherein the at least three pins extend outward from the depression.31. The screwdriver of claim 30, wherein at least one of the at leastthree pins comprises a protuberance on the inner surface.
 32. Thescrewdriver of claim 28, wherein the first central axis does notintersect any portion of any of the at least three pins.
 33. Thescrewdriver of claim 28, wherein a cross-section of at least one of theat least three pins is circular.
 34. The screwdriver of claim 28,wherein the at least three pins abut an outer edge of the head.
 35. Thescrewdriver of claim 28, wherein at least one of the at least three pinsis retractable into the shank.